Red Hat Bugzilla – Bug 1303728
Seeing VM crash while writing in same RBD Disk from different VMs
Last modified: 2017-07-30 11:36:16 EDT
Description of problem: While trying to write on a same RBD image, the VM is getting crashed. Version-Release number of selected component (if applicable): rpm -qa | grep ceph ceph-common-0.94.5-4.el7cp.x86_64 ceph-osd-0.94.5-4.el7cp.x86_64 ceph-0.94.5-4.el7cp.x86_64 ceph-radosgw-0.94.5-4.el7cp.x86_64 ceph-debuginfo-0.94.5-4.el7cp.x86_64 ceph-selinux-0.94.5-4.el7cp.x86_64 Selinux as enforcing. How reproducible: Steps to Reproduce: 1. Create an rbd image with --feature 13, create snap and clone it. 2. Attach the same Clone to 2 different VMs. 3. Try to write on the RBD clone from 2 different VMs at same time Used dd to write it. Actual results: Lock should handle this use case, and there should not be a crash Expected results: Seeing the VM Crash. Additional info: Logs attached.
I discussed this with Jason and Josh, and the outcome is that we want to land a fix in 0.94.7 upstream and give it plenty of testing before pulling it downstream. This is not technically a valid use case of RBD exclusive locking, and customers should never have two VMs using the same RBD image at the same time. If customers had such a setup, this would certainly cause other issues. Jason and Josh also confirmed that there's no way to hit this with a single client, nor during a VM live migration between hypervisors. Since this is a lower priority bug, re-targeting to RHCS 1.3.3.
This was resolved in RHCS 2.x